“I hope, then, that you will build the chimneys in the new house in such a way that they will not smoke. You know that Marie would be much vexed if they should.”
“We will do our best; and the local conditions are favourable to begin with; we are not commanded by other elevations, we have not any eddies of wind to fear; along the plateau on which we are building the breezes are regular. Moreover, we have only straight high roofs, and all the flues rise above the ridges. We shall build these flues with brick, and make them of ample size. Nothing obliges us to give them very oblique directions; they rise vertically, or nearly so. Lastly, we shall have a system of air-flues, arranged from the very foundations, in a cool aspect; for that must be attended to, since if the air-flues are open to the south—for example—the air they receive from without, even during the winter, is warmer than that of the room where the fire is lighted; and then the air-flue draws the smoke which comes down into the room. At least the fire cannot be lighted; the wood is only charred, and does not burn.
“At Paris they often have a single flue for several fireplaces (arranged one over the other), and parallel with it a ventilation-flue sending a branch to each of these fireplaces. That is a good plan, especially in houses where there are as many as five fireplaces, one over the other; because the weakening of the walls by the juxtaposition of a number of flues is thus avoided. The fires exercise a reciprocal attraction, and this system prevents smoke in the rooms. These flues must have a section sufficient for all the fireplaces—that is, for five ordinary chimneys, one above another, a section of 1 foot 9 inches superficial, or 16 inches square. But here, where we have only three stories and sufficient room, I prefer having separate flues for each chimney; especially as with the system of single flues all the fires must be lighted: which is always the case in a large town. If they are not, it will happen in rapid changes of temperature that the smoke will pass into one of the higher or lower fireplaces instead of following the vertical column. This inconvenience, which by the by is only accidental, is remedied by well-arranged dampers.”
“But,” said Paul, “does not this cold air of the air-channel chill the apartments?”
“This cold air comes into the fireplace itself, not into the apartment; it is evident that if a fire is not made, the air-flue introduces cold air, which contributes to lowering the temperature of the apartment. It may be shut off by a damper. But keep this in mind: to make a fire burn wood, or coal, or anything else, oxygen is needed. You have learned that in your studies in chemistry and physics. Air, therefore, is required; without air no fire. Formerly they did not take the trouble to provide air-flues for fireplaces, because the air came into the rooms under the doors and through the ill-closed windows, and also because the apartments being very large contained air enough to keep up a fire for some time. And our grandfathers’ chimneys, be it observed, smoked pretty considerably. We of the present day are less hardy, and like to have smaller rooms, well shut in, and we are afraid of draughts; that is all very well, but the chimney must have a draught, since without it the fuel will not burn and therefore not warm you. It is evident that this column of cold air, which you call in to stimulate the combustion, takes with it, in ascending the flue, a considerable amount of heat. Many plans have therefore been devised for preventing the heated air from passing rapidly away. It is caused to turn in the flues, and obliged to remain as long as possible, or at least to leave in the walls of the numerous passages which it traverses a part of the heat it has absorbed. These passages in their turn warm a surrounding cavity or room, which is also supplied with air. This air, dilated by heat, tends to escape. Issues are made for it, which are called hot-air escapes. This is the principle of the hot-air apparatus.”
“A propos of heating apparatuses,” said Madame de Gandelau, “are you intending to construct one in the new house?”
“Certainly; its place is marked on the plan of the cellars below the entrance hall, and its flue goes up in the interior angle of the great staircase. A heating apparatus is indispensable in a country house, especially if it is not lived in throughout the winter. It is the means of preventing a good deal of injury to the house. Heating once or twice a week during the cold and damp season is sufficient to keep the apartments fairly dry.”
“Do you not think the heat of the hot-air apparatus injurious to health?”
“The warm air issuing from the heating apparatus is unwholesome, because in becoming warm it has lost a part of its oxygen, and because oxygen is as necessary to us in supporting life as it is to fuel in supporting combustion. We can avoid some of the injurious results to the animal economy arising from the deoxidized air by making it pass over basins filled with water on leaving the heat receiver; but this means is only palliative, and we thus lose part of the warmth.
“I consider hot-air apparatuses desirable only for warming apartments that are not lived in, such as entrance-halls, staircases, and passages; but if hot-air escapes are provided in drawing-rooms, dining-rooms, and bedrooms, care must be taken not to allow them to be open while the apartments are occupied. Open them only to dry the rooms when you are absent; and when this is done, open the windows, and close the hot-air escapes when you shut the windows.”